One time programmable (OTP) electrically programmable read only memory (EPROM) can be an effective, low cost mechanism for providing non-volatile memory in a variety of computer related applications, such as in small handheld digital devices like cellular telephones, personal digital assistants (PDAs), etc.
A one time programmable EPROM cell generally comprises a transistor that can be programmed once so that a particular amount of charge is stored within the cell, where the amount of charge stored within the cell corresponds to digital data (i.e., 0 or 1). An OTP transistor is programmed by applying a first known voltage to the cell, and the data stored within the cell is read basically by applying a second different voltage to the cell and reading a resulting current that flows through the cell. A first amount of current generally corresponds to a logic 1, while a second amount of current generally corresponds to a logic 0.
OTP EPROM cells may be utilized to store configuration data, for example, in electronic devices. It can be appreciated that it is desirable for such data to remain continually accessible over long periods of time, such as for up to several years, for example. However, aspects of conventionally designed OTP transistors provide for weak spots that can result in electrical tunneling, which can cause a charge stored within an OTP transistor to diminish over time, which can lead to erroneous or false data reads.
Accordingly, it would be desirable to design an OTP transistor based EPROM cell in a manner that mitigates weak spots and resulting adverse effects associated with tunneling phenomena.